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Case Study: Misleading Dye Test

Type of Pool:

Vinyl Liner

Equipment Used:

Dye Tester Cones, Pressure Testing Equipment, Electronic Listening DeviceLeakalyzer

Pool with leak detection equipment

Situation:

Customer reported that pool was losing water and suspected the skimmer line.

Solution:

Based on the customer’s suspicion we started out leak job by running  a dye test of the skimmer lines right away using the dye testing cones. The deep end skimmer was plugged while the shallow end skimmer was tested and vice versa. Both skimmers pulled dye.  Since each skimmer had its own run from the pump, and since we had isolated each line by closing valves we thought that both lines had a leak.

In order to start pinpointing those leaks, we first pressurized the line with air from the deep end skimmer back to a closed valve at the equipment. We could immediately hear the bubbling noise of air escaping into water saturated soil right below the skimmer bowl.

Then, we checked the shallow end skimmer line by switching to inducing pressure from that skimmer bowl. There was no noise and a much slower pressure drop. After listening for a while but still not finding a noise and not seeing a significant pressure drop, we switched to inducing pressure from the valves to isolate each line individually. Using this approach the shallow end skimmer line held pressure and the deep end line made noise in the same spot we had heard before.

Pressure testing from pool equipment

It turns out that the shallow end skimmer line was not leaking, but it had drawn dye through the pipes to the other skimmer break due  valves that didn’t seal off properly. Pressure testing helped us determine that there was just the one leak, not two.

We also ran a Leakalyzer test on the shell of the pool while the lines were plugged.  The results confirmed that the pool shell wasn’t losing water. We left the job having given the customer a clear leak location and the assurance that their pool would no longer be leaking once the plumbing repair was made.

Highlights:

  • Leaks can siphon through bad valves, which produces unclear results when dye testing. It’s important to understand how your tests may give deceptive information and perform secondary tests if you are left with any uncertainty. Pressure testing was able to verify the line was good despite drawing dye.
  • Opening the pump lid would have been an effective method of isolating the skimmers by creating an air break. Since the dye test was done early in our Initial Assessment we hadn’t yet opened the pump.

Case Study: New Pool, Big Leak

Type of Pool:

Vinyl Liner

Equipment Used:

Leakalyzer, LeakTrac, Dye Tester Cones, Pressure Testing Equipment, Electronic Listening Device, Hydrophone, Tube Level

Situation:

We were called to examine a new build that was losing 4” of water per day. It hadn’t been leaking for the first four days that it was filled but recently started rapidly losing water. When we arrived to the pool the water level was down below the skimmers, but the skimmer bowls were still full of water – indicating that those lines were not leaking.

Solution:

Suspecting that the problem was in a plumbing line, we did a quick dye test of the returns and cleaner line with the dye testing cones, but they also were not drawing water. Our Leakalyzer test had been running during these initial observations, and indicated a loss of 3.5 inches per day. A quick scan with the LeakTrac showed no leaks in the liner, so it was time to dive down to the main drain. A dye test with the dye testing cones showed that line was the source of our water loss.

We then plugged the main drain lines while we were diving and ran a pressure test from the equipment back to the pool. The water pressure test confirmed the line was leaking, so we then started inducing air for sonic location. It took a while for the air to reach the leak, indicating that the leak wasn’t close to the equipment where the air was being induced. So, we used a hydrophone attached to our XLT30H listening device to start listening along the main drain lines where they ran close to the shell of the pool. We could hear the loud bubbling/gurgling noise of air escaping into water saturated soil near the base of the wall in the middle of the deep end.

Since the main drains were plugged we ran another Leakalyzer test to verify that the rest of the pool shell was not losing water and the main drain line was the only issue.

A main drain leak at the base of the wall is not a repair anyone wants to make, so to verify the sonic leak location we used a tube level. We attached a clear plastic tube to the end of a standard open plug in the main drain. Now, instead the leak draining water from the pool it drained the water in the tube. The tube leaked down to the level of the leak and then stopped. We colored the water in the tube with Leakmaster Fluorescent Dye to be able to clearly see the water level. The water level stopped right at the level that we had identified with the hydrophone.

The crew dug up the leaking plumbing line and found a stake had been driven through the pipe!?!

Highlights:

  1. A hydrophone with digital sound graph is helpful when listening for main drain plumbing leaks through the shell of the pool.
  2. The Leakalyzer helps verify the rest of pool isn’t leaking while pressure testing and pinpointing leaks in plumbing.
  3. A simple tube level can help verify the depth of the leak before digging. Be creative with the materials you have on hand!

Troubleshooting Underground Pipe Leaks

 

There is no question that pinpointing underground pipe leaks in swimming pool plumbing can be tricky, especially when first starting out. While many different scenarios pose many different challenges, generally issues with pinpointing leaks fall into one of two categories:

  1. Not hearing a noise
  2. Hearing a noise in a large area and having trouble narrowing it down

Below are a few solutions to these common issues.

If You Can’t Hear A Noise:

First of all, don’t overlook just turning up the volume on your listening device. This can often be the fix for deeper leaks. However, more often than not adjusting your technique to make the correct leak noise is the solution to the problem. Remember, the noise you’re trying to achieve is a distinct bubbling gurgling noise that comes from air escaping through the leak into water saturated soil. For a refresh of the basics of this technique check out our “Pipe Leak Location” slideshow in the Resource Center. Below are the two most common problems that keep you from making a good leak noise.

1. Air is not reaching the leak

Even though air is being induced into the plumbing, it may not be reaching the leak due to leftover water in the pipe. Especially if the leak is on the bottom of the pipe or in a lower section of the plumbing it can take a long time for the induced air to push all the water out of the leak. Remember that water in the pipe will stay at the bottom of and in low sections of plumkbing.  Air can only reach the leak if all of the water above leak level has been purged from the line. Only once you’re sure that air is escaping from the leak is it time to start listening. There are two ways to be more confident that air is reaching the leak:

  • One way to be sure air is reaching the leak is to remove the lowest plug from the line and completely purge all the water out of the line with air before reinstalling the plug and building air pressure. Since the location of the leak and how the plumbing runs is unknown at this point this can be a time-saving solution.
  • Another way to make sure air has reached the leak is to slowly push the remaining water out through the leak by inducing air into the line. Once enough water has been pushed out and air starts escaping from the leak you’ll see a dramatic drop in pressure on your pressure gauge. This happens because air escapes from a leak faster than water does, so when the air reaches the leak that cushion of air escapes rapidly . . producing the telltale pressure drop. Once this happens it’s time to start listening. On top of not having to remove and then replace plugs, another benefit to this approach is that you further saturate the soil outside of the leak, producing a better environment for a better noise. For safety, always watch the pressure gauge so that too much pressure doesn’t build up.

2. The soil is not saturated with water

Once you know that air has reached the leak, if you still can’t hear a noise you may be dealing with a situation where the soil is not saturated enough with water. If this is the case there are a few options:

  • The first option would be to saturate or re-saturate the soil by inducing more water into the pipe and letting it escape out through the leak. Once the soil is saturated, switch back to inducing air and listen with your listening device.
  • If you are in a situation where there has been washout or the pipe is in gravel-y soil it can be difficult to maintain saturation outside of the pipe.  In this case a technique of inducing water from the lower end of the plumbing and air from the high end with the goal of making them meet at the leak can make a great noise. You will need two means of inducing pressure, but this is a technique that can be quite effective.  This is often used on big breaks in lines where you can’t even build up pressure. If it is a smaller leak; take extra care to not build up too much pressure, this would be an indication that water is being put into the line faster than it is escaping and that air can no longer reach the leak . If you see the pressure gauge rising reduce the rate of water flow into the line.

If You Hear A Noise Everywhere:

Many times the leak noise is so loud that it can be heard in a large area, so honing in on the precise location is a challenge. Like above, volume controls can help. Just turning the volume down can reduce the area in which you can hear the leak. Also adjusting the amount of air being induced might give us a more distinct or crisp bubble or gurgle sound. If you’re still hearing the noise in a large area, these are some things to keep in mind as you listen:

  • The noise should be loudest AND clearest where the leak is. As you listen, don’t just look for loudest but also the clearest sound.  Just as sound levels soften the further you get away, sounds also begin to muffle and aren’t as clear the further you get from the spot.
  • Find and mark the outer edges of the sound area. As you move around you will eventually see a drop off in noise volume. Marking these boundaries can give you a good visual of where the center or source of the leak noise is.
  • Using the Frequency Filters on your XLT30 or XLT17 is one of the best ways to hone in on the leak sound. These filters provide significant help in reducing the search area, minimizing background noise and helping us hear a clear and distinct sound. For more detailed information on using filters check out this blog post.

Case Study: Eliminating Misleading Leak Sounds

Type of Pool:

Vinyl Liner

Equipment Used:

Leakalyzer, Pressure Testing Equipment, XLT30HHydrophoneDye

Situation:

Customer reported that the pool was leaking 1-2 inches per day and that a new liner was installed recently. When we arrived, the pool level had already dropped below the skimmers and returns.

Solution:

We ran a pump on and pump off test with the Leakalyzer and found the pool was losing slightly more water with the pump off. This indicated that we should suspect suction side plumbing. Since the pool water level was already below the skimmers we dove down to check the main drains. A dye test confirmed that the main drain line was drawing dye from both of the two main drains.

We set up our pressure testing equipment to start pinpointing the location of the leak and ran a quick pressure test with water first to confirm that what the dye was showing was accurate. Once we started inducing air and purged all the water from the line we were able to hear a good leak noise in two spots with the Hydrophone (attached to the XLT30H). The first noise was right at one of the main drain bowls and the other was in a corner of the pool. While we had the main drain lines plugged we also ran another Leakalyzer test, which verified the water loss had stopped in the pool so there was no need to run a LeakTrac on the liner or dye test the fittings, skimmers, etc.

In order to determine which noise we were hearing was actually the leak, we slid an inflatable plug 8’ into the line from the main drain bowl and re-pressure tested. The pressure test still failed, so we knew the leak had to be farther than 8’ away from the main drain bowl. With this information we decided that the place we heard noise in the corner of the pool was the leak location. Another confirming factor was that while we were inducing air, there would occasionally be a bubble that came up behind the liner to the surface of the pool. Before leaving we also ran pressure tests on skimmer and returns to verify the rest of the plumbing was good.

Learnings:

  1. Pressure testing helped us identify actual problem when the  noise was heard in multiple locations.
  2. Leakalyzer verified that pool shell was leak free, saving us time during the isolation phase.

Understanding Frequency Filters on Electronic Listening Devices

Ever have trouble honing in on an underground pipe leak?  Understanding how to use the frequency filters on an electronic listening device can greatly increase accuracy in underground pipe leak location.  Once the correct noise is being made at the leak and the volume of the listening device is set properly, adjusting the frequency filters can provide a great advantage in identifying the leak sound and pinpointing the exact location.

Inducing air into a leaking underground plumbing line will produce a sound right at the leak’s location where the air escapes into water saturated soil. This noise at the leak is a distinct gurgling noise that produces sounds in most of the audible frequency ranges. Understanding those frequencies can help identify the exact location of the pipe leak.  To illustrate this idea, think of a leak noise like a choir.  In a choir you hear the song being sung as a whole but it is made up of different parts: sopranos (high frequencies), altos, tenors and bases (low frequencies).  Manipulating the filters on an XLT17 or XLT30H can focus in on a specific frequency and which is beneficial for eliminating background noise and zeroing in on the leak.

How to identify which frequency range to choose  has to do with how sounds travel.  Low frequency sounds travel further than high frequencies. This is evident at an outdoor concert.  Approaching the concert from a long ways away, the first noise that you’ll hear is the base due to its low frequency. The other higher frequency ranges aren’t heard until getting closer to the stage – the source of the sound. When listening for a leak noise, starting on a low frequency allows us to hear noises in a broader area. Then, once a leak noise is identified in a broad area, switching to a higher filter blocks out the lower frequencies in order to get closer to the leak.

Filtering can also help limit unwanted background noise in order to hear the sound of the leak more distinctly. Often times the hum of an air conditioner, electrical noise, or even cars on a freeway can be distracting when listening for a swimming pool pipe leak.  While unfortunately there is no “air conditioner button”, by using the frequency filters to block out the frequency range that is most distracting, the leak noise we’re listening for becomes clearer.  The XLT30H even has a specific adjustable notch filter for this purpose.

In general the leak noise should be the loudest right on top of the leak. In addition to being loud the leak noise will also be the most clear or distinct right over the leak.  Sound waves will get muffled or disrupted the further they have to travel.  Like at the outdoor concert, the overall sound may be heard from farther away than the actual words being sung. Listen not just for the loudest noise but the clearest and most distinct sound.

It takes time to play around with the different filtering options in order to understand how they impact leak noise. If you’re just getting started with leak detection, take some extra time during your next sonic location to play around with the filters on your listening device. Every job is also a learning opportunity!


Case Study: Persistence Pays Off

 

Type of Pool:

Gunite Spa/Pool

Equipment Used:

LeakalyzerXLT30H, Hydrophone ,Dye, Ridgid Inspection Scope,  Ridgid Micro Drain Reel, Pressure Testing Equipment, Dye Testing Cones

Situation:

The customer called because their pool would leak down to the tile line and stop, so they wanted us to locate the leak and asses the tile line to determine if a full renovation was needed. When we got to the pool the water level was filled to the normal level as we requested, but the customer pointed out where it would typically leak down to which was an inch below the skimmer, but a couple inches above the jets. It seemed as though we were in for a quick tile line crack location and putty repair.

Solution:

We ran a Leakalyzer test to get a better understanding of how fast the pool was losing water and while doing so started listening with a hydrophone to the suspected tile line. A quick trip around the pool with the hydrophone didn’t uncover any suspect areas. We moved on to dye testing because sometimes small leaks don’t make enough noise for the hydrophone. After dye testing the whole tile line we were able to confirm that there were no leaks in the shell of the pool at the level where the water drained down to. It turns out this job was going to be a little more complicated than we thought!

We checked our ongoing Leakalyzer test which was showing a current rate of over 20” per day of water loss (small pool, big leak). To do a quick check of the plumbing lines we used the Dye Tester Cones and learned that the jet returns drew dye like crazy. Because the water level stopped higher than the jets we began to suspect the blower line instead of the jet return line. A pressure test confirmed the suspected line was leaking as we couldn’t even build any pressure. A Leakalyzer test with the jet returns plugged confirmed the rest of the pool was not losing water, so we knew we could be done with any further testing in the shell of the pool.

Since the equipment pad was positioned lower than the pool, in order to induce air from the high side of the plumbing we had to use one of the jet returns. When we started listening with the XLT30H there was a loud noise right above where we were inducing pressure that actually seemed to echo throughout the pool. There were two places that seemed louder and more distinct than the other areas though: the jet fitting and a place where the pipes presumably ran underneath the pool. We deduced that even though we were inducing from the high side of the plumbing, since the leak was in the blower line the air had to travel through remaining water in the jet line, creating some of and perhaps all the noise we were hearing. To confirm this suspicion, we switched and induced pressure from the other side of the plumbing. After this switch the sound in those two locations went silent. This confirmed we were hearing the sound of air traveling through remaining water in the pipe and not air escaping out of the leak into water saturated soil.

The lack of noise around the pool forced us to look closer to the equipment which would mean that the leak had to be well below where the water level stopped.  It turned out there was a Hartford Loop for the blower line, but it wasn’t high enough and thus didn’t stop water from draining back through until the water level reached the familiar point on the tile.  We suspect someone made a modification to the blower plumbing at some point for aesthetic reasons and buried the loop without understanding its purpose.

Building enough pressure for a quick sonic location was difficult and since we had easy access to the flexpipe  we used a Ridgid Micro Drain Scope and a line locator to pinpoint the exact location. About 15 feet in we saw what appeared to be a cracked pipe due to freeze damage.

To verify the crack we saw was our leak, water was induced into the blower line from the high side of the plumbing and we pulled that camera back towards the low side of the plumbing watching for the water flow to stop.  Sure enough the water was flowing into this crack.  The crack was dye tested with extension tubing from Anderson Manufacturing affixed to the end of the camera. The dye was drawn into the crack a well. The crack was about 8’ long and on both sides of the pipe – so no wonder we couldn’t build pressure!

Learnings:

  1. Just because water stops at the tile line doesn’t mean it’s the tile line that’s leaking!
  2. Inducing pressure from both ends of plumbing can be a way to verify if you’re hearing a leak noise vs air traveling through water in pipe. If noise is only audible when you induce from one end it may be standing water in the pipe not air escaping into water saturated soil.
  3. Dye Tester Extension Tubing can be taped to inspection cameras for leak verification or location.
  4. Persistence paid off, but this one was a bit misleading and ended up being time consuming. Some leaks are more tricky than others!

 


Case Study: Thin Ground Probes are Necessary for Deep Leaks

Type of Pool:

Vinyl / In-ground

Equipment Used:

Leakalyzer, XLT30H Bigfoot and Ground Probes, Hydrophone, Pressure Testing Kit, Dye

Situation

We received a call about a pool that had just had a new liner installed, but was still losing lots of water. The customer suspected the water loss was in the main drain line. When we arrived to the pool the Leakalyzer confirmed the reported water loss.

Solution

The main drain lines were plumbed separately up to the equipment, so we put an open plug in each of the main drains to see if they would draw dye. One line did, but the other did not. To confirm, we pressure tested the line that drew dye with water and it failed. In order to pinpoint the exact location of the leak, we then induced air into the line and began to listen with the hydrophone for a leak under the pool, but didn’t hear any significant noises. We then switched to using the Bigfoot microphone with the XLT30H to listen through the concrete around the pool and still didn’t hear anything that indicated the leak location. Only when we started using the XLT30H ground probes in the soil between the pool deck and the equipment were we able to get close enough to the leak to pick up a great noise and find the exact location of the leak.

Learnings

  1. Thin ground probe rods included with the XLT30H make it possible to get the probe deep into ground to absorb leak sound vibrations.
  2. Turning air pressure off and back on once hearing the leak location confirms the noise is the one we are making.

Case Study: Listening Devices Pinpoint Even the Deepest Leaks

 

Equipment Used:

XLT30, Pressure Testing Kit , Leakalyzer

Situation:

The customer noticed that a lot of sand was being blown into the pool and that there were bubbles in the air filter, so a problematic skimmer line was isolated and shut off.  However, even after closing and plugging that problematic skimmer line there were still sand and bubbles being blown back into the pool.

Sand in pol from leaking skimmer return line.

Solution:

When we arrived to the pool, the skimmer line was plugged and a Leakalyzer test with the pump off showed no water loss. That made us suspect that at least the portion of the plumbing below water level was good. We then pressure tested the other two skimmer lines to confirm the whole line was good and they held pressure. The main drain was eliminated as the source of a problem without getting in the water through our Leakalyzer test that covered the plumbing below the water line and an air lock test that included the line that was above water level. Eliminating all of these other areas left us to examine the problematic skimmer line as the only potential problem. Upon further inspection, the valve used to shut off the line wasn’t holding, which explains the continued bubbles and sand in the pool even after the line was taken out of use.

To determine the specific location of the leak within the faulty skimmer line, we induced air into water saturated soil to listen with the XLT30. At first the bubbling and gurgling sound of a leak was faint, but just by turning the volume up on the XLT30 we were able to identify a distinct noise where the leak was. It was fairly easy tonarrow the leak location down to a 6’ diameter, but in order to get down to within 2’ of the leak we needed to use the advanced filtering capabilities of the XLT30. Once the high filter was turned on, there was a clear spot with the most distinct noise. As sound waves travel they get more and more muffled, so the sound will be crispest and most distinct right over the leak. The sound did fade a little as time went on, but re-saturating the soil by inducing more water into the line revitalized the sound.

The customer estimated that the skimmer line was 18” to 2’ deep, but when we cut the concrete and dug down to that level there wasn’t any moisture or pipe. To confirm we were in the right place we turned the pressure back on and still heard the leak so kept digging and finally found the broken pipe at just over 4’ deep. Before we replaced the cracked fitting we cut the pipe and pressure tested both ways to assure the rest of the line was good.

Digging in concrete deck for plumbing leak

Learnings (are there any key takeaways or learnings from how this leak was found?):

  • Combining a Leakalyzer test with an air lock test of the main drain can confirm that line is solid without getting into the pool.
  • If you notice a once strong leak noise fading, you may just need to add more water to re-saturate the soil.
  • Trust your equipment! If you’re confident you heard a leak in a specific place, you may have to dig farther than expected to find it, but it will be there.

Pressure Testing Myths Busted

Pressure testing is a topic where a number of myths and misunderstandings have developed in the swimming pool industry. Below, we explain the truth behind 4 common misconceptions that should help you stay focused on efforts that will lead to leak detection success and profits.

MYTH #1: Pressure Testing is Unnecessary for Leak Detection

While you may be able to find common leaks without pressure testing, if you want to leave the pool assured that you have found all of the leaks . . . and you want to give the customer that assurance, pressure testing is critical.

There are other ways of finding easy to reach leaks in plumbing, but from the standpoint of conclusively determining if the entire line is leak free, nothing beats a properly performed pressure test.  Furthermore, despite advancements in cameras and other probes that have applications in some situations, the most common and dependable way of pinpointing leaks underground involves the use of a listening device that picks up the sound of pressurized air escaping from a leak into water saturated soil.

MYTH #2:  Air Can Be Used Interchangeably With Water for Pressure Testing

Air and water behave very differently in pressure testing situations.  Understanding three pressure testing principles that address these differences is important as you determine when to use air and when to use water to build pressure.

  1. Air compresses under pressure, water does not
  2. Air stays at the top of the pipe, water stays at the bottom
  3. Air escapes from leaks faster than water does

Our pressure testing slide show provides helpful diagrams and more explanation of how these principles affect your test results.  As a general rule it is best to use water when testing to determine if the line is leaking since it does not compress under pressure so it will show a loss in pressure quickly, even with a small loss in volume.  On the other hand, air trapped in a line can expand as water volume is lost from the leak, slowing (and sometimes completely masking) a drop in pressure. Additionally, if plugs happen to pop out under pressure they will come out with much less force if the line is pressurized with only water . . . trapped air will propel a popped plug like a cannon ball!

The main benefit of using air is that it makes a much better noise escaping from the pipe into water saturated soil than water does.  So, once you have identified a leaking section of plumbing with a water test, switch to air to produce a good noise that can be picked up by your listening device.

Myth #3: Air and Water Can Be “Mixed” in a Pressure Tester and Will Stay “Mixed” Inside the Pipe

We’ve debunked this myth by testing it on a plumbing system made of clear PVC.  Regardless of how they are transmitted into the pipe, water stays low and air stays high.  They do not stay mixed up just because they are put under pressure.  This is simple physics and anyone who says otherwise is selling you hocus-pocus.

Adding both air and water to a line is not the first step you should take when trying to make a good leak noise.  While it is indeed important for the soil to be full of water outside of the pipe where air will blow out through the leak, no noise is made unless air actually gets to the leak.  Since water stays at the bottom of the pipe and air at the top, if the leak is in the low end of the plumbing no air will get to it if you are adding both air and water.  So, all of the water above the leak level must be purged from the line before this happens. Generally this is best accomplished by removing a low plug and blowing air from the high end.  Once you see bubbles, replace the plug, set your air source regulator to maintain no higher than 5 psi, and begin listening.  Larger leaks and/or leaks in soil that drains quickly may necessitate adding water while air is going into the line.  To avoid noises inside the pipe, do this with a separate pressure tester from the low end of the plumbing.  The best results happen when air and water do not mix inside the plumbing . . . just at the leak!

MYTH #4: Certain Kinds of Gas Make Better Noises Than Others for Leak Location

Any gas escaping from a leak will make bubbling/gurgling /hissing/spotting sounds in the full range of sonic frequencies that can be picked up with a listening device.  Sometimes, leak detectors will use nitrogen tanks to deliver the gas into the line quietly (without the conflicting sound of a compressor).  However, these tanks are used not because of any special characteristic of the gas (in fact, the air we breathe is made up of 78% nitrogen) but because of its ease of availability and inexpensiveness in relation to other gasses.  SCUBA tanks adapted with an adjustable regulator can also be used if you can get them filled.  A small compressor works just fine for inducing air pressure, especially if you use a 50 foot hose that allows you  to position the compressor some distance from where you are listening.

In some situations where soil or leak conditions make it difficult to create a noise helium gas is used to find underground plumbing leaks.  In these situations a Helium Detector picks up the presence of the gas as it makes its way to the soil’s surface.  Helium is not being used because it makes a better noise, but because it can be detected by this detector.

If you have any questions about pressure testing or swimming pool leak detection, consult the Resource Center of our website or give us a call.


What makes a top notch listening device?

When it comes those tough underground plumbing leaks, electronic listening devices are the backbone of the leak detection industry.   While there are other methods the most reliable and consistent method is to make a noise at the leak with pressurized air escaping into water saturated soil, then listen for where the noise is coming from.  This noise can sometimes be picked up by just an open ear but often a listening device is needed to help amplify the sound and filter out other noises to focus in on leak sound and pinpoint location.

Choosing the right listening device for your company is an important decision. When researching a product purchase, similar to listening for a leak, there can be a lot of “noise” to sift through.  Here at Anderson Manufacturing we have combined research and testing with the experience of hundreds of pool leak detection professionals to find and keep the best option for a swimming pool leak listening device.

While there are many factors to think about such as cost, dependability and service after the sale. There are also some more technical criteria to consider when looking at purchasing a swimming pool leak listening device.   Since listening devices range from your standard geophones to sophisticated technology here are some tips for what criteria to look at.

Important criteria to consider when comparing listening devices:

Sensitivity – how well the device amplifies sounds from the transmitting material 

Frequency Range – how broadly the device can hear all the sounds created by a leak

Filtering – how effectively the device can filter out background noise enabling  you to focus on a leak sound

The Bigfoot microphone for the XLT30H reduces outside noise interference.
The Bigfoot microphone for the XLT30H reduces outside noise interference.
Sensitivity

The standard ground microphones that come with Fisher’s XLT17 and the XLT30H listening devices, use piezoelectric microphones because these are known to be the best type of microphone to use in situations where sounds are being picked up from liquids or solids.  Virtually every company that makes serious equipment for locating underground plumbing leaks for municipal work incorporates piezoelectric technology. Accessing the technological knowledge of those who have experience in this area is one reason we have chosen to work with Fisher and utilize their products.  This type of equipment requires more specialized expertise than standard microphone amplification (that used for music/voice etc.).

In practice you will find that sensitivity by itself however is not the only important performance criteria.  Most any device will be able to amplify a sound to the point that it will hurt your ears.  What’s more important is hearing the right sound and distinguishing it from background noise.  That’s where the other two important criteria come into play.

 

Frequency Range

Both pressurized underground plumbing leaks and static shell leaks in the pool make noises in a wide range of frequencies depending on a variety of conditions.   We like to think of the sounds a leak makes in the same way we do instruments in an orchestra.  You want to be able to hear everything from the shrillest piccolo to the deepest tuba.  Although every leak is different, as general rule underground plumbing leaks make sounds in the lower frequency ranges while static leaks in the shell of the pool are in the higher range.  If your listening device doesn’t pick up sounds at the top or bottom of this range you will be missing the fullness of the sound a leak makes or you may miss it altogether.  Both the Fisher XLT17 and XLT30H pick up sounds in a frequency range of 20Hz to 6000Hz.  In addition, the XLT30H includes a switch that enables the unit to work effectively both when sounds are in the low range (for underground leaks picked up by the Bigfoot microphone) and the higher ranges (for underwater leaks picked up by the hydrophone).

 

Filtering Capability

The final performance criteria, and what we consider to be the most important for swimming pool applications, is an area where Fisher devices particularly shine over all others we have researched.  A listening devices filter allows you to specifically highlight (or eliminate) a specific range of sounds.  Consider for instance that we only wanted to hear the violins in the orchestra of leak sounds we imagined above.  Filtering is important because the devices are so sensitive that we will likely hear other sounds around the pool (it always seems as though the next door neighbor want to mow their grass when you’re trying to find a leak!).  The filter helps us zero in on the leak sound without being distracted by the background noise.  Additionally, different ranges of sound behave differently underground or underwater.  Low frequency sounds travel much further than high frequency sounds.  By selecting high frequency sounds once a leak sound has been identified the frequency filter can help in pinpointing leaks to a small area.

 

Fisher devices provide a wide range of filtering options to address most any scenario. The Band Pass filter allows selection of a narrow band of frequency anywhere in the range of sound.  The Hi Pass filter focuses high frequency sounds providing adjustment of the low end of this range.  The Low Pass filter does the opposite – focusing on the low end and providing an adjustable high end..  The XLT30H also includes a Notch Filter that allows the elimination of a specific frequency range (for instance to minimize the “hum” of a nearby air-conditioner) and can be used at the same time as the other filters.

 

Another noise minimizing feature available on Fisher devices is especially important when the unit is used for listening to pipes in the ground.  The Bigfoot muffler utilized by Fisher to minimize outside noises transmitted through the air is the best we’ve seen.  This rubber boot deadens outside noises preventing them from reaching the sensitive piezoelectric microphone which makes direct contact with the pool deck or ground through a heavy aluminum foot.

 

Conclusion

Ultimately, we are convinced, that Fisher Listening Devices as sold by Anderson Manufacturing Co. are the most technologically advanced, well rounded tool for all types of swimming pool acoustical leak location   They have been continually improved through the years and currently represent the best package for addressing pool leak problems in both the plumbing and shell.  We back our belief with the evidence of thousands of successful customers and a satisfaction guarantee that promises your money back if you are not satisfied with their performance.

If you have made it this far through this you have taken in a lot of information, hopefully it has been helpful in making decisions that will affect your leak detection success.  Remember you can always call and talk through the buying process or for technical help regarding a leak or leak detection equipment. Thanks for reading!

 


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